Protein Core Abstract: Dr. Matsuo will direct the Protein Core and a staff of two full-fime scientists. The Protein Core will service the Program Project entitled Crifical Interactions of APOBECSs: Molecular Approaches to Novel HIV Therapies by: (i) purifing isotope-labeled and non-labeled proteins from E. coli for use by all program investigators and (ii) purifing proteins from human HEK29S cells for use by all program invesfigators. All proteins will be tested for purity and activity prior to distribution.